An understanding of the factors behind the evolution of multicellularity is one of today’s frontiers in evolutionary biology. This is because multicellular organisms are made of one subset of cells with the capacity to transmit genes to the next generation and another subset responsible for maintaining the functionality of the organism, but incapable of transmitting genes to the next generation. The question arises: why do somatic cells sacrifice their lives for the sake of germline cells? How (...) is germ/soma separation maintained? One conventional answer refers to inclusive fitness theory, according to which somatic cells sacrifice themselves altruistically, because in so doing they enhance the transmission of their genes by virtue of their genetic relatedness to germline cells. In the present article we will argue that this explanation ignores the key role of policing mechanisms in maintaining the germ/soma divide. Based on the pervasiveness of the latter, we argue that the role of altruistic mechanisms in the evolution of multicellularity is limited and that our understanding of this evolution must be enriched through the consideration of coercion mechanisms. (shrink)

Reprogramming of somatic cells to a pluripotent state holds huge potentials for regenerative medicine. However, a debate over which method is better, somatic cell nuclear transfer (SCNT) or induced pluripotent stem (iPS) cells, still persists. Both approaches have the potential to generate patient‐specific pluripotent stem cells for replacement therapy. Yet, although SCNT has been successfully applied in various vertebrates, no human pluripotent stem cells have been generated by SCNT due to technical, legal and ethical (...) difficulties. On the other hand, human iPS cell lines have been reported from both healthy and diseased individuals. A recent study reported the generation of triploid human pluripotent stem cells by transferring somatic nuclei into oocytes, a variant form of SCNT. In this essay, we discuss this progress and the potentials of these two reprogramming approaches for regenerative medicine. (shrink)

The case of Andrew Gobea, the first child to receive experimental gene therapy for SCID, and a reflection on the associated ethical implications of gene therapy research.

The prelude to successful human somatic gene therapy, i.e. the efficient transfer and expression of a variety of human genes into target cells, has already been accomplished in several systems. Safe methods have been devised to do this using non‐viral and viral vectors. Potentially therapeutic genes have been transferred into many accessible cell types, including hematopoietic cells, hepatocytes and cancer cells, in several different approaches to ex vivo gene therapy. Successful in vivo gene therapy requires improvements (...) in tissuetargeting and new vector design, which are already being sought. Gene‐transfer protocols have been approved for human use in inherited diseases, cancer and acquired disorders. Althouth the results of these trials to date have been somewhat disappointing, human somatic cell gene therapy promises to be an effective addition to the arsenal of approaches to the therapy of many human diseases in the 21st century if not sooner. (shrink)

Recent arguments on the ethics of stem cell research have taken a novel approach to the question of the moral status of the embryo. One influential argument focuses on a property that the embryo is said to possess—namely, the property of being an entity with a rational nature or, less controversially, an entity that has the potential to acquire a rational nature—and claims that this property is also possessed by a somatic cell. Since nobody seriously thinks that we have (...) a duty to preserve the countless such cells we wash off our body every day in the shower, the argument is intended as a reductio ad absurdum of the claim that the embryo should be afforded the same moral status as a fully developed human being. This article argues that this argument is not successful and that it consequently plays into the hands of those who oppose embryonic stem cell research. It is therefore better to abandon this argument and focus instead on the different argument that potentiality, as such, is not a sufficient ground for the creation of moral obligations towards the embryo. (shrink)

Despite the progress achieved over the last decade after the birth of the first cloned mammal, the efficiency of reproductive cloning remains invariably low. However, research aiming at the use of nuclear transfer for the production of patient‐tailored stem cells for cell/tissue therapy is progressing rapidly. Yet, reproductive cloning has many potential implications for animal breeding, transgenic research and the conservation of endangered species. In this article we suggest that the changes in the epi‐/genotype observed in cloned embryos arise (...) from unbalanced nuclear reprogramming between parental chromosomes. It is probable that the oocyte reprogramming machinery, devised for resident chromosomes, cannot target the paternal alleles of somatic cells. We, therefore, suggest that a reasonable approach to balance this asymmetry in nuclear reprogramming might involve the transient expression in donor cells of chromatin remodelling proteins, which are physiologically expressed during spermatogenesis, in order to induce a male‐specific chromatin organisation in the somatic cells before nuclear transfer. BioEssays 30:66–74, 2008. © 2007 Wiley Periodicals, Inc. (shrink)

Somatic cell nuclear transfer (SCNT) remains a controversial technique, one that has elicited a variety of regulatory responses throughout the world. On March 29, 2005, Canada's Assisted Human Reproduction Act came into force. This law prohibits a number of research activities, including SCNT. Given the pluralistic nature of Canadian society, the creation of this law stands as an interesting case study of the policy-making process and how and why a liberal democracy ends up making the relatively rare decision to (...) use a statutory prohibition, backed by severe penalties, to stop a particular scientific activity. In this article, we provide a comprehensive and systematic legal analysis of the legislative process and parliamentary debates associated with the passage of this law. (shrink)

We examine whether the current regulatory regime instituted in South Korea and the United States would have prevented Hwang’s potential transgressions in oocyte procurement for somatic cell nuclear transfer, we compare the general aspects and oversight framework of the Bioethics and Biosafety Act in South Korea and the US National Academies’ Guidelines for Human Embryonic Stem Cell Research, and apply the relevant provisions and recommendations to each transgression. We conclude that the Act would institute centralized oversight under governmental auspices (...) while the Guidelines recommend politically-independent, decentralized oversight bodies including a special review body for human embryonic stem cell research at an institutional level and that the Guidelines would have provided more vigorous protection for the women who had undergone oocyte procurement for Hwang’s research than the Act. We also suggest additional regulations to protect those who provide oocytes for research in South Korea. (shrink)

The extent to which normal (nonmalignant) cells of the body can evolve through mutation and selection during the lifetime of the organism has been a major unresolved issue in evolutionary and developmental studies. On the one hand, stable multicellular individuality seems to depend on genetic homogeneity and suppression of evolutionary conflicts at the cellular level. On the other hand, the example of clonal selection of lymphocytes indicates that certain forms of somatic mutation and selection are concordant with the (...) organism-level fitness. Recent DNA sequencing and tissue physiology studies suggest that in addition to adaptive immune cells also neurons, epithelial cells, epidermal cells, hematopoietic stem cells and functional cells in solid bodily organs are subject to evolutionary forces during the lifetime of an organism. Here we refer to these recent studies and suggest that the expanding list of somatically evolving cells modifies idealized views of biological individuals as radically different from collectives. (shrink)

Emerging evidence suggests that microRNA (miRNA)‐mediated post‐transcriptional gene regulation plays an essential role in modulating embryonic stem (ES) cell pluripotency maintenance, differentiation, and reprogramming of somatic cells to an ES cell‐like state. Investigations from ES cell‐enriched miRNAs, such as mouse miR‐290 cluster and human miR‐302 cluster, and ES cell‐depleted miRNAs such as let‐7 family miRNAs, revealed a common theme that miRNAs target diverse cellular processes including cell cycle regulators, signaling pathway effectors, transcription factors, and epigenetic modifiers and shape (...) their protein output. The combinatorial effects downstream of miRNA action allow miRNAs to modulate cell‐fate decisions effectively. Furthermore, the transcription and biogenesis of miRNAs are also tightly regulated. Thus, elucidating the interplay between miRNAs and other modes of gene regulation will shed new light on the biology of pluripotent stem cells and somatic cell reprogramming. (shrink)

Mos, a protein kinase, is specifically expressed and functions during meiotic maturation (or G2/M progression) of vertebrate oocytes. When expressed ectopically, however, it can also readily induce oncogenic transformation (or uncontrolled G1/S transitions) in somatic cells. In both of these cell types, Mos activates mitogen‐activated protein kinase (MAPK), which seems largely to mediate its different functions in both oocyte maturation and cellular transformation. In oocyte maturation, the Mos‐MAPK pathway probably serves to activate and stabilize M‐phase promoting factor (MPF) (...) (possibly by inhibiting some negative regulator(s) of this factor), while in cellular transformation, it seems to stabilize and activate the nuclear oncoprotein c‐Fos as well as to induce transcription of its gene. Thus, the different functions of Mos in oocytes and somatic cells may arise chiefly from its different MAPK‐mediated targets in the respective cell types. This review discusses the cellular basis that may enable Mos to act differently in oocytes and somatic cells. (shrink)

The mammalian egg employs a wide spectrum of epigenome modification machinery to reprogram the sperm nucleus shortly after fertilization. This event is required for transcriptional activation of the paternal/zygotic genome and progression through cleavage divisions. Reprogramming of paternal nuclei requires replacement of sperm protamines with canonical and non‐canonical histones, covalent modification of histone tails, and chemical modification of DNA (notably oxidative demethylation of methylated cytosines). In this essay we highlight the role maternal histone variants play during developmental reprogramming following fertilization. (...) We discuss how reduced maternal histone variant incorporation in somatic nuclear transfer experiments may explain the reduced viability of resulting embryos and how knowledge of repressive and activating maternal factors may be used to improve somatic cell reprogramming. (shrink)

Under certain conditions, the cell cycle can be arrested for a long period of time. Vertebrate oocytes are arrested at G2 phase, while somatic cells arrest at G0 phase. In both cells, nuclei have lost the ability to initiate DNA synthesis. In a pair of recently published papers,1,2 Méchali and colleagues and Coué and colleagues have clarified how frog oocytes prevent untimely DNA synthesis during the long G2 arrest. Intriguingly, they found only Cdc6 is responsible for the (...) inability of immature oocytes to replicate DNA. Cdc6 is a key component for replication licensing, and for G0 cells to re‐enter the proliferative stage. Strikingly similar strategies for preventing the untimely replication in both cells suggest that the suppression of replication licensing is a universal mechanism for securing the prolonged arrest of the cell cycle. BioEssays 25:313–316, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

The majority of higher plants (including almost all important crops) demonstrate strict uniparental maternal inheritance of plasmagenes in the process of conventional sexual crossing; it is therefore impossible to generate heterozygosity for these genes with standard crossing procedures. However, recent experiments have shown that hybrid plants can be produced by somatic cell fusion and that these contain the cytoplasmic genes of both parents. The phenotypic and genetic properties of these hybrid plants are described here.

Cellular interactions in the mammalian ovarian follicle between its germ‐line and somatic cell components are crucial for its development and function. These interactions are mediated by both membrane gap junctions and paracrine factors. Somatic cell‐to‐oocyte communication is essential for oocyte growth and the regulation of meiotic maturation. In particular, granulosa cells provide nutrients and molecular signals that regulate oocyte development. Oocytes, on the other hand, promote the organization of the follicle, the proliferation of granulosa cells, and (...) the differentiation and function of cumulus cells, a subset of granulosa cells. Determining the nature of the oocyte‐to‐granulosa cell signals remains a key challenge for future work. (shrink)

An important feature of male fertility is the physiological priming of spermatozoa by a multifaceted process collectively referred to as capacitation. The end point of this evasive process is the hyperactivated spermatozoa capable of binding to terminal sugar residues on the egg's extracellular coat, the zona pellucida (ZP), and undergoing acrosomal exocytosis (i.e., induction of the acrosome reaction). The hydrolytic action of acrosomal enzymes released at the site of zona binding, along with the enhanced thrust generated by the hyperactivated beat (...) pattern of the bound spermatozoa, are important factors that regulate the penetration of ZP and fertilization of the egg. Despite many advances in identifying sperm components that promote capacitation, the mechanism underlying the calcium‐triggered process remains elusive. The purpose of this review article is to focus on new advances that have enhanced our understanding of in vivo/in vitro capacitation, a prerequisite event resulting from a dramatic modification and reorganization of the sperm membrane molecules. Special emphasis has been laid on accumulating evidence suggesting potential similarities between the sperm capacitation and early phases of calcium‐triggered membrane fusion (i.e., tethering and docking) during secretory and endocytotic pathways among eukaryotes. BioEssays 26:281–290, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

It is now clear that two prominent nuclear domains, interchromatin granule clusters (IGCs) and Cajal bodies (CBs), contribute to the highly ordered organization of the extrachromosomal space of the cell nucleus. These functional domains represent structurally stable but highly dynamic nuclear organelles enriched in factors that are required for different nuclear activities, especially RNA biogenesis. IGCs are considered to be the main sites for storage, assembly, and/or recycling of the essential spliceosome components. CBs are involved in the biogenesis of several (...) classes of small RNPs as well as the modification of newly assembled small nuclear RNA. We have summarized data on the molecular composition, structure, and functional roles of IGCs and CBs in the nuclei of mammalian somatic cells and oocytes of some animals with a special focus on insects. We have focused on similarities and differences between the IGCs and CBs of oocytes and the well‐studied CBs and IGCs of cultured mammalian somatic cells. We have shown the heterogeneous character of oocyte IGCs and CBs, both in structure and molecular content. We have also demonstrated the unique capacity of oocytes to form close structural interactions between IGC and CB components. We proposed to consider these joint structures as integrated entities, sharing the features of both IGCs and CBs. (shrink)

Somatic cell count is a diagnostic test of milk for mastitis in cows. Its specificity and sensitivity are less than 1.0, making test results uncertain. I discuss epistemological problems of the test such as underdetermination, undercalibration and underdiscrimination, in the solution of which biomedical and economic factors may play a role. Diagnostics of the SCC should be considered as an epistemological network, functioning in a network in which farmers, veterinarians, epidemiologists and milk industry shift their position following biomedical, technological (...) and economic changes, which is described as an actor-network to understand how human and non-human agents in mastitis may be associated. (shrink)

The somatic mutation theory has been the prevailing paradigm in cancer research for the last 50 years. Its premises are: (1) cancer is derived from a single somatic cell that has accumulated multiple DNA mutations, (2) the default state of cell proliferation in metazoa is quiescence, and (3) cancer is a disease of cell proliferation caused by mutations in genes that control proliferation and the cell cycle. From this compelling simplicity, an increasingly complicated picture has emerged as more (...) than 100 oncogenes and 30 tumor suppressor genes have been identified. To accommodate this complexity, additional ad hoc explanations have been postulated. After a critical review of the data gathered from this perspective, an alternative research program has been proposed. It is based on the tissue organization field theory, the premises of which are that carcinogenesis represents a problem of tissue organization, comparable to organogenesis, and that proliferation is the default state of all cells. The merits of these competing theories are evaluated herein. BioEssays 26:1097–1107, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

The stunning possibility of “reprogramming” differentiated somatic cells to express a pluripotent stem cell phenotype (iPS, induced pluripotent stem cell) and the “ground state” character of pluripotency reveal fundamental features of cell fate regulation that lie beyond existing paradigms. The rarity of reprogramming events appears to contradict the robustness with which the unfathomably complex phenotype of stem cells can reliably be generated. This apparent paradox, however, is naturally explained by the rugged “epigenetic landscape” with valleys representing “preprogrammed” (...) attractor states that emerge from the dynamical constraints of the gene regulatory network. This article provides a pedagogical primer to the fundamental principles of gene regulatory networks as integrated dynamic systems and reviews recent insights in gene expression noise and fate determination, thereby offering a formal framework that may help us to understand why cell fate reprogramming events are inherently rare and yet so robust. (shrink)

Determinations of the ethical acceptability of genetic therapy have relied on several distinctions in attempts to separate ethically acceptable genetic therapy from those possible therapies that could lead to genetic modifications of future human beings. One distinction that has been proposed is that genetic modifications of human somatic cells is ethically acceptable but that Germ-Line genetics modifications would be ethically objectionable. This paper examines several serious difficulties which call into question the ethical relevance of a somatic/Germ-Line distinction. (...) Keywords: double effect, future generations, Germ-Line modification CiteULike Connotea Del.icio.us What's this? (shrink)

The somatic integration definition of life is familiar from the debate on the determination of death, with some bioethicists arguing that it supports brain death while others argue that some brain‐dead bodies exhibit sufficient somatic integration for biological life. I argue that on either interpretation, the somatic integration definition of life implies that neither the preimplantation embryo nor the postimplantation embryo meet the somatic integration threshold condition for organismal human life. The earliest point at which a (...) somatic integration determination of life could be made would be the beginning of the fetal stage, 9 weeks postfertilization. Bioethical implications are considered, specifically with respect to the moral status of the postimplantation embryo in embryo research and abortion. (shrink)

ABSTRACT This paper examines three arguments that use the concept of potential to identify embryos that are morally suitable for embryonic stem cell research (ESCR). According to the first argument, due to Ronald Green, the fact that they are scheduled for disposal makes embryos left over from IVF treatments morally appropriate for research. Paul McHugh argues that embryos created by somatic cell nuclear transfer differ from those that result directly from the meeting of sperm and egg in having potential (...) especially conducive to the therapeutic use of their stem cells. I reject both of these arguments. According to the way of making distinctions in embryonic potential that I defend, it is the absence of a functional relationship with a womb that marks embryos morally suitable for ESCR. (shrink)

Clonal disease is often regarded as almost synonymous with cancer. However, it is becoming increasingly clear that our bodies harbor numerous mutant clones that are not tumors, and mostly give rise to no disease at all. Here we discuss three somatic mutations arising within the hematopoietic system: BCR‐ABL, characteristic of chronic myeloid leukemia; mutations of the PIG‐A gene, characteristic of paroxysmal nocturnal hemoglobinuria; the V617F mutation in the JAK2 gene, characteristic of myeloproliferative diseases. The population frequencies of these three (...) blood disorders fit well with a hierarchical model of hematopoiesis. The fate of any mutant clone will depend on the target cell and on the fitness advantage, if any, that the mutation confers on the cell. In general, we can expect that only a mutation in a hematopoietic stem cell will give long‐term disease; the same mutation taking place in a cell located more downstream may produce just a ripple in the hematopoietic ocean. (shrink)

The aim of this paper is to assess the relevance of somatic evolution by natural selection to our understanding of cancer development. I do so in two steps. In the first part of the paper, I ask to what extent cancer cells meet the formal requirements for evolution by natural selection, relying on Godfrey-Smith’s (2009) framework of Darwinian populations. I argue that although they meet the minimal requirements for natural selection, cancer cells are not paradigmatic Darwinian populations. (...) In the second part of the paper, I examine the most important examples of adaptation in cancer cells. I argue that they are not significant accumulations of evolutionary changes, and that as a consequence natural selection plays a lesser role in their explanation. Their explanation, I argue, is best sought in the previously existing wiring of the healthy cells. (shrink)

Harvesting human embryonic stem (hES) cells is a highly controversial field of research because it rests on the destruction of human embryos. Altering the procedure of nuclear transfer (NT) is suggested to generate hES cell lines without ethical obstacles by claiming that no embryo would be involved. While discussing the nature of an embryo and related central questions concerning their moral status and the respect they deserve, this paper argues that the entity created by somatic cell nuclear transfer (...) (SCNT) or altered nuclear transfer (ANT) is an embryo and has the same moral status as a natural embryo. Respect for the embryo is expressed by the ethical principles of proportionality, probability and subsidiarity. This paper argues that the human embryo should only be taken for research with high ranking goals, which are proven in animal experimentation and for which there are no alternatives. This makes ANT obsolete and shows that SCNT to produce hES cells is premature at the present time. (shrink)

In multicellular organisms, cells are frequently programmed to die. This makes good sense: cells that fail to, or are no longer playing important roles are eliminated. From the cell’s perspective, this also makes sense, since somatic cells in multicellular organisms require the cooperation of clonal relatives. In unicellular organisms, however, programmed cell death poses a difficult and unresolved evolutionary problem. The empirical evidence for PCD in diverse microbial taxa has spurred debates about what precisely PCD means (...) in the case of unicellular organisms. In this article, we survey the concepts of PCD in the literature and the selective pressures associated with its evolution. We show that definitions of PCD have been almost entirely mechanistic and fail to separate questions concerning what PCD fundamentally is from questions about the kinds of mechanisms that realize PCD. We conclude that an evolutionary definition is best able to distinguish PCD from closely related phenomena. Specifically, we define “true” PCD as an adaptation for death triggered by abiotic or biotic environmental stresses. True PCD is thus not only an evolutionary product but must also have been a target of selection. Apparent PCD resulting from pleiotropy, genetic drift, or trade-offs is not true PCD. We call this “ersatz PCD.”. (shrink)

Restrictions on research on therapeutic cloning are questionable as they inhibit the development of a technique which holds promise for succesful application of pluripotent stem cells in clinical treatment of severe diseases. It is argued in this article that the ethical concerns are less problematic using therapeutic cloning compared with using fertilised eggs as the source for stem cells. The moral status of an enucleated egg cell transplanted with a somatic cell nucleus is found to be more (...) clearly not equivalent to that of a human being. Based on ethical considerations alone, research into therapeutic cloning should be encouraged in order to develop therapeutic applications of stem cells. (shrink)

Somatic mutation plays a key role in transforming normal cells into cancerous cells. The analysis of cancer progression therefore requires the study of how point mutations and chromosomal mutations accumulate in cellular lineages. The spread of somatic mutations depends on the mutation rate, the number of cell divisions in the history of a cellular lineage, and the nature of competition between different cellular lineages. We consider how various aspects of tissue architecture and cellular competition affect the (...) pace of mutation accumulation. We also discuss the rise and fall of somatic mutation rates during cancer progression. BioEssays 26:291–299, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

According to the somatic mutation theory (SMT), cancer begins with a genetic change in a single cell that passes it on to its progeny, thereby generating a clone of malignant cells. It is strongly supported by observations of leukemias that bear specific chromosome translocations, such as Burkitt's lymphoma, in which a translocation activates the c‐myc gene, and chronic myeloid leukemia (CML), in which the Philadelphia chromosome causes production of the BCR‐ABL oncoprotein. Although the SMT has been modified and (...) extended to encompass tumor suppressor genes, epigenetic inheritance, and tumor progression through accumulation of further mutations, perhaps the strongest validation comes from the successful treatment of certain malignancies with drugs that directly target the product of the mutant gene.magnified imageDavid Vaux is at the Walter and Eliza Hall Institute and La Trobe Institute for Molecular Science, Melbourne, Australia. (shrink)

The use of a reporter gene in transgenic mice indicates that there are many local mutations and large genomic rearrangements per somatic cell that accumulate with age at different rates per organ and without visible effects. Dissociation of the cells for monolayer culture brings out great heterogeneity of size and loss of function among cells that presumably reflect genetic and epigenetic differences among the cells, but are masked in organized tissue. The regulatory power of a mass (...) of contiguous normal cells is expressed in its capacity to normalize the appearance and growth behavior of solitary homophilic neoplastic cells, and to redirect differentiation of solitary heterophilic stem‐like cells. Intimate contact between the interacting cells is required to induce these changes. The normalization of the neoplastic phenotype does not require gap junctional communication between cells, though transdifferentiation might. These varied relationships are manifestations of the unifying biological principle of “order in the large over heterogeneity in the small”. BioEssays 28: 515–524, 2006. © 2006 Wiley Periodicals, Inc. (shrink)

The commercial provision of putative stem cell-based medical interventions in the absence of conclusive evidence of safety and efficacy has formed the basis of an unregulated industry for more than a decade. Many clinics offering such supposed stem cell treatments include statements about the ‘ethical’ nature of somatic stem cells, in specific contrast to human embryonic stem cells, which have been the subject of intensive political, legal, and religious controversy since their first derivation in 1998. Christian groups—both (...) Roman Catholic and evangelical Protestant—in many countries have explicitly promoted the medical potential and current-day successes in the clinical application of somatic stem cells, lending indirect support to the activities of businesses marketing stem cells ahead of evidence. In this article, I make a preliminary examination of how the structures and belief systems of certain churches in South Korea and the United States, both of which are home to significant stem cell marketing industries, has complemented other factors, including national biomedical funding initiatives, international economic rivalries, permissive legal structures, which have lent impetus to a problematic and often exploitative sector of biomedical commerce. (shrink)